1. Field of the Invention
The present invention relates to organosilicon compounds having an isocyanate group which is masked by a blocking agent, to processes for preparing them, to processes for eliminating the blocking agents, and to the use of the organosilicon compounds.
2. Background Art
Organofunctional silanes, i.e., compounds which contain an organic functional group as well as a silyl group, have acquired industrial significance in a wide variety of applications, for example as adhesion promoters, as crosslinkers, and for modifying surfaces. Of particular importance in this context is the isocyanate functionality, which on account of its high reactivity toward protic compounds such as alcohols, amines, oximes and the like, is able to react in diverse ways.
Frequently, however, when isocyanates are used in an aqueous environment or in isocyanate-crosslinking one-component paint systems, a masked form of an isocyanate is required in order to prevent unwanted premature reaction of the isocyanate. For this purpose use is frequently made industrially of isocyanates whose isocyanate group has been blocked with a moiety which is thermally facile (D. A. Wicks, Z. W. Wicks, PROG. ORG. COAT. 1999, 36, 148-172). These blocked isocyanates masked by a blocking agent are frequently easy to prepare and, furthermore, exhibit a markedly reduced toxicity in comparison to that of the corresponding free organic isocyanate.
Some organosilicon compounds containing masked isocyanate groups are known, for example from DE 34 24 534 A1, EP 0 212 058 B1, JP 08 291186 and JP 10 067787. Common to all of these compounds, however, is the fact that between the masked isocyanate group and the silyl group there is a propylene group, as a result of which the reactivities with respect to hydrolysis and condensation are comparatively low. As a consequence, relatively high temperatures are frequently necessary for the reaction of these compounds, which leads in turn to the blocking agent being eliminated at an unwanted point in time. As a result, these compounds are totally unsuitable for many applications, or at least have great disadvantages.